Programs for performing desired data processing, including basic programs, such as, above all, operating systems (OS), various programming languages, simplified program languages or word processeors, or the basic data indispensable for these programs, such as dictionary data, pattern data for Chinese characters or parameter data for pattern recognition, although not in need of being rewritten in a manner distinct from a variety of general data that are to be processed, occasionally require some form of write inhibit processing, in order to prevent inadvertent rewriting of the contents by mistaken operation. To this end, in a magnetic disk, such as a so-called floppy disk, the basic program or the basic data are protected by specifying the possible presence of write inhibition for each file by a software technique. However, the write protection implemented by the software technique may be cancelled rather easily by the software such that writing on a file specified for write inhibition may occasionally occur during, for example, program runaway or upon the occurrence of software errors. Therefore, for more reliable protection, a disk having the program and the basic data recorded thereon is provided as a so-called program disk separately from the data disk and a write inhibit measure such as a mechanical or hardware technique employing a so-called protect seal or protect notch is frequently applied to the program disk in its entirety.
It is noted that, as disclosed, for example, in the Japanese Pat. Publication KOKAI No. 100249/1983, there has been proposed an optical information recording carrier which is provided with signal tracks composed of pits dedicated to reproduction for facilitating adjustment of the recording/reproducing optical system.
Recently, a recording medium having an extremely high recording density, such as an opto-magnetic disk, has made its debut. With an optical disk having ultra-high recording density, it is not an effective utilization of the disk's recording capacity to prepare a disk dedicated to a program file to inhibit writing thereon. The basic program such as the aforementioned OS is formed by tens to hundreds of kilobytes, whereas the basic data is usually formed of hundreds of kilobytes, so that, even when several basic programs and data are recorded in combination, a recording capacity on the order of several megabytes suffices. However, an optical disk usually has a recording capacity amounting to several hundreds of megabytes, which is larger by approximately a hundred times than that required for the basic data or program. Therefore, when an optical disk is non-rewritably set as a so-called program disk, recording uses only a small portion of the recording capacity, while the remaining major portion is not used for recording, which is not economical. Therefore, one must resort to designating the write inhibit for each file for protection against mistaken writing by a software technique, which has a drawback in that it has an insufficient protection capability against software errors, as mentioned above.
On the other hand, various other copy inhibit measures are used to prevent duplication without authorization. However, the risk remain extremely high that the program disk will be duplicated and illicitly used by other than the authorized users with the aid of a copy program.
The present invention has been made with the above in mind and is intended to provide an optical disk wherein an erasure program for the record regions of the disk is nonrewritably recorded on a writable optical disk, along with the software program or basic data, to realize powerful write protection for the software program or the basic data, while inhibiting the duplication of the disk without authorization.